EVAP Canister Check

1. Canister Purge
2. Vapor
3. Vent

An improperly functioning EVAP canister can cause problems with engine driveability and/or vehicle refueling. The canister can become plugged (with some internal obstruction or liquid fuel) or develop an air leak.

Stalling or poor driveability can be caused by:

1. Fuel saturated canister. Disconnect the EVAP canister purge line at the underbody (near the fuel filter/regulator) and look for liquid fuel in the line.
   Fig 1: EVAP Canister Purge Line

   Courtesy of GENERAL MOTORS CORP.
   • If liquid fuel is present, install a siphon hose on this line and attempt to draw out more fuel.
     NOTE: If liquid fuel is present, the canister must be replaced.
   • If fuel is in the canister, investigate the vapor venting of the system. Refer to DIAGNOSING FUEL FILL PROBLEMS .
2. No canister purge function. Check DTC codes for PO446 and refer to FAULT ISOLATION article.

   Evidence of fuel loss or fuel vapor odor can be caused by:

   • Cracked or damaged EVAP canister.
   • Fuel saturated EVAP canister (evaluate as noted above).